The present application is based on Patent Application No. 11-333750 filed in Japan, the content of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an illumination optical system, and specifically relates to an illumination optical system provided with a polarization light conversion optical system. The present invention further relates to a projector which uses this illumination optical system for projecting an optical image on a screen.
2. Description of the Related Art
Conventional projectors are known which illuminate an optical image formed by an image display element such as a liquid crystal panel or the like in accordance with a projection image signal, and project this illuminated optical image on a screen via a projection lens. In such a projector illumination optical system, conventionally a triangular prism type polarization beam splitter is used in the polarization conversion optical system. The triangular prism type polarization beam splitter has been a chief factor preventing the design of light weight liquid crystal projectors due to the heavy weight of the right angle prism included therein.
The present applicant(s) have disclosed, in U.S. Pat. No. 6,005,655, a construction which provides divided prism to reduce the weight of the right angle prism, and positions the prism ridgeline at the boundary of the lens cell of a first lens array comprising an optical integrator so as to prevent the projection of the unsharp image of the ridgeline on the screen.
There is demand for lighter weight and less expensive projectors, and it follows that the polarization conversion optical system in the illumination optical system must be made lighter in weight with reduced cost.
An object of the present invention is to provide an improved illumination optical system.
A specific object of the present invention is to provide a light-weight and less expensive illumination optical system for the polarization conversion optical system.
A further object of the present invention is to provide a light-weight and low cost projector.
These objects are attained by an illumination optical system and a projector provided with same, the illumination optical system comprising:
a light source;
a lens array for splitting the light from the light source into a plurality of beams of light;
a polarized light conversion optical system having a separator and converter, wherein the separator has a prism array comprising a plurality of right angle prisms arranged consecutively with the same surface being an inclined surface for reflecting the plurality of beams of light by the inclined surface and separating the plurality of reflected beams of light into first and second linearly polarized light beams having mutually intersecting polarization directions, and the converter converts the polarization direction of one of the first and second linearly polarized light beams to the other polarization direction;
and wherein the lens cell width of the lens array is greater than the prism array pitch of the prism array viewed from the incidence side of the plurality of beams of light.